In recent years, a light-weight, thin-walled, and highly-rigid member are being demanded as a housing of laptop computers. As a molded product formed with a view to achieving lightness, thinness, and high rigidity, for example, there is a carbon-fiber-reinforced molded product produced by laminating carbon fiber prepregs and curing the laminated carbon fiber prepregs.
However, because the carbon fiber prepregs contain a semi-cured thermosetting resin, the thermosetting resin becomes completely cured in a comparatively short period of time when stored at a normal temperature. For this reason, carbon fiber prepregs are difficult to handle, which raises a problem of an increase in cost for manufacturing a carbon-fiber-reinforced molded product using carbon fiber prepregs.
Patent Document 1 discloses a fiber reinforced product manufactured by stacking a plurality of sheets of fiber reinforced layers, each of the sheets having carbon fibers aligned in the same fiber direction, such that the respective fiber directions are arranged in a specific manner. However, since the fiber reinforced layer having an aligned fiber direction is very expensive, there is a problem of an increase in cost of a fiber-reinforced molded product as the number of fiber reinforced layers is increased. Moreover, the fiber-reinforced molded product has a specific gravity of about 1.6, which had not been sufficient in terms of weight reduction of components of a housing of a laptop or the like.
Patent Document 2 discloses a sandwich structure having a core material including voids, and a fiber reinforced material including continuous carbon fibers and a matrix resin and provided on both surfaces of the core material. However, this has not been sufficient from the viewpoint of thickness reduction and high rigidity required for a housing member of a portable device like a laptop.
Patent Document 1: JP 2004-209717 A
Patent Document 2: WO 2006/028107 A1